Step 1: Prepare Seafood - In a skillet, melt 2 tablespoons of butter over medium heat, add minced garlic and sauté for about 1 minute. Add lobster and crab meat and cook for 2-3 minutes until warmed through, then transfer to a bowl.

Step 2: Mix Filling - In the same bowl, combine seafood mixture with cream cheese and half of the shredded mozzarella. Season with salt and pepper, then blend until smooth and creamy.

Step 3: Cook Pasta - Bring a large pot of salted water to a boil, add jumbo pasta shells and cook for approximately 8-10 minutes until al dente, then drain and cool slightly.

Step 4: Make Sauce - In the skillet, melt remaining 2 tablespoons of butter, whisk in flour until bubbly. Gradually stir in heavy cream and remaining cheeses until smooth.

Step 5: Assemble - Preheat oven to 375°F (190°C). Spread a layer of creamy sauce at the bottom of a baking dish. Fill each pasta shell with seafood mixture and place in dish, pour remaining sauce over the top.

Step 6: Bake - Cover baking dish with foil and bake for 20 minutes. Remove foil and bake for an additional 10 minutes until golden brown.

Step 7: Serve - Let cool for a few minutes, garnish with extra parmesan or herbs if desired, and serve warm.